This invention relates generally to surgical cannulas, and more particularly to a laparoscopic cannula which provides a fluid-tight seal around laparoscopic instruments of various outer diameters.
In medical procedures such as laparoscopy the patient's abdomen is distended to allow access to and visibility of the abdominal cavity. In order to distend the abdominal cavity a gas is injected into the cavity at a pressure of about 12 torr. The gas insuflates the abdominal cavity, supporting the abdominal walls up and away from the internal organs. Without this maintained pressure the abdominal wall collapses and all visibility through the laparoscopic camera is lost.
While the abdomen is distended with gas, cannulas through which medical instruments can be inserted traverse the abdominal wall. Valves are typically included in these cannulas to prevent air from leaking from the pressurized cavity when the laparoscopic cannula is in use. The competence of these valves is of great importance because even a small leak in the cannula may cause a decrease in insuflation pressure and the attendant collapse of the abdominal wall.
A variety of laparoscopic instruments are used with such cannulas. For example, laparoscopic forceps, clamps, scalpels, etc., are all known. These laparoscopic instruments are typically round in cross section, and have outer diameters ranging from about 2 mm to about 1 cm. In many laparoscopic procedures it is necessary to remove a larger laparoscopic instrument and to replace it with a smaller instrument during the course of the procedure. It is not practical to replace the cannula at such times.
Laparoscopic cannulas are available with lumen diameters of 5 mm, 1 cm, etc., with the larger sizes being preferred for laparoscopic procedures in which larger-diameter laparoscopic instruments may be required. The valve employed in the cannula may be any valve which seals around medical instruments, such as a slit valve, etc. However, all single-valve systems are known to leak when the smallest laparoscopic instruments are used in large-lumened cannulas.
Presently, the insertion of small instruments into the 1 cm or larger cannulas requires a reducing gasket to prevent significant air loss. In the larger cannulas of the prior art, such as the TROCAN.TM. 5 mm Disposable Surgical Trocar and Cannula No. 004536-901, the reducing gasket is a plastic cap which is inserted over the outer opening of the cannula to reduce the effective size of the opening. It can be appreciated that changing the reducing gasket is a time-consuming inconvenience to the medical team since the gasket must pass from the nurse to the doctor before being applied to the cannula. The time and effort required to change prior art gaskets is an undesirable aspect of such devices.
A need therefore exists for a universal cannula which may rapidly be adapted to accept laparoscopic instruments of varying sizes and to provide a fluid-tight seal around such instruments. The present invention addresses this need. Furthermore, the present invention has applicability in other surgical procedures such as cardiological procedures involving inserting guide wires, catheters and other medical devices into a medical patient's blood vessels or other body cavities.